U.S. Pat. No. 7,153,446 provides a fire or explosion suppression agent, having two suppressant parts, one comprising an explosion suppressing chemical substance which is substantially liquid at normal temperatures and pressures and the other comprising a fire or explosion suppressing inert gas; the chemical substance being dispersed as a suspension in the inert gas, the chemical substance when so disposed having low environmental impact, with a short atmospheric lifetime of less than 30 days; the chemical substance comprising one or more specific halogenated chemicals. It is not clear whether the fire or explosion suppression agent is released before or after the fire is initiated. The description mentions only the protection of a specified space or volume such as the interior of a vehicle or a volume within an aircraft.
EP 562756 discloses a fire extinguishing and explosion suppression agent comprising perfluorohexane discharged in atomised form, such as, for example, by means of a pressurising gas which may, for instance, be nitrogen at least partially dissolved in the perfluorohexane. It is clear from page 4 lines 23+ that the discharge of the suppressant is triggered by detection of a rise in pressure due to incipient explosion.
U.S. Pat. No. 7,090,028 discloses a method and apparatus for producing an extremely fine micron and sub-micron size water mist using an electronic ultrasonic device that produces the mist at ambient-pressure and delivering the mist for application in suppressing fire. From column 6 lines 50+ it is understood that the mist delivery is made after the beginning of the fire.
WO 99-24120 describes a fire or explosion suppressant comprising water or an aqueous alkali metal salt solution together with a surfactant. The surfactant is selected so as to be fast-acting that is, so that upon dispersion of the water or water-based solution towards the fire or explosion (e.g. in a jet or under atomisation), the surfactant acts to produce a surface tension value which becomes low (preferably at least as low as about 25 mN/m) within the time taken for the dispersed water to reach the fire or explosion (less than 50 and preferably less than 20 milliseconds). The fire or explosion suppression agent is released after the fire is initiated.
WO 98-47572 describes an explosion suppression arrangement for suppressing explosions within a protected area, comprising containing means for containing explosion suppressant material and having an outlet normally closed by frangible means, a source of pressure, pressure distribution means positioned within the containing means so as to be located within explosion suppressant material therein, the distribution means being pressurised by the source upon activation thereof so as to pressurise the suppressant material and break the frangible means to cause discharge of the suppressant material through the outlet. Upon detection of an explosion in the area, the material is discharged into the area and suppresses the explosion. The explosion suppressant material is a powder such as mono-ammonium phosphate or sodium hydrogen carbonate.
US 2003-0000951 provides a method for reducing the severity of vapor cloud explosions in partially confined operating areas, comprising placing porous, high surface-area-to-volume ratio protective material in the area in sufficient amount to reduce the pressure effects caused by ignition of the flammable vapor clouds. According to a preferred embodiment the protective material is a metal mesh or foil material. Examples relate to prevent explosion of a drum containing pentane. The protective material is an expanded aluminum foil, 20 to 80 μm in thickness, of density 30 to 50 kg/m3 and low volumetric displacement (1 to 2%). Said expanded aluminum foil arranged in rolls is inserted in the drum.
U.S. Pat. No. 5,495,893 discloses a deflagration suppression system, which is particularly applicable to deflagrations involving combustible gases. The deflagration suppressant in the system is typically water which is dispersed in the combustible gas as a stream of droplets having a Sauter mean Diameter of no more than about 80 microns. The system can include a combustible substance detector to detect potentially explosive concentrations of a combustible substance, such as the combustible gas, before the onset of a deflagration. By detecting the concentration of a combustible substance in a defined region, the sensing means are able to detect a condition in the defined region that is conducive to the occurrence of a deflagration before a deflagration actually occurs. The dispersing means are thus able to disperse a stream of liquid droplets in the defined region before the occurrence of a deflagration and thereby reduce the likelihood of a deflagration occurring in the defined region.
All these above prior arts don't relate to unconfined vapor cloud explosions.
U.S. Pat. No. 5,096,679 relates to a system to mitigate the effect of an environmental release of a contaminant gas. More particularly, it relates to a system to control the spread of a contaminant gas cloud released into the environment. Specifically, it relates to a system to diffuse and/or neutralize the contaminant gas cloud rendering it less hazardous to the surrounding environment. To elaborate on this aspect, said prior art relates to a system having a plurality of fluid effect devices capable of diffusing, diluting and diverting a cloud of contaminant gas; and further capable of chemically altering the contaminant gas to render it environmentally safe. A method for mitigating the effect of the contaminant gas release also is provided. This prior art is mainly concerned with release of chemicals such as hydrogen fluoride. It mentions introduction of calcium carbonate into a cloud of hydrogen fluoride that in this manner will cause a chemical reaction, thus forming calcium fluoride, a non-toxic mineral precipitate easily absorbable by the ground environment.
This prior art relates to the release of a non flammable contaminant in the environment but is silent on the method to mitigate the consequences of an unconfined or partially confined vapor cloud explosion.
All the prior art is dealing with flame extinguisher or suppression to prevent explosions. The devastating potential of a VCE comes from the acceleration of the flame through the unburnt cloud. The higher the flame speed the higher the overpressure. Under certain circumstances the deflagration can undergo a DDT (Deflagration to Detonation Transition). The current invention consists of introducing a product (or mixture) in the cloud that will avoid acceleration of the flame. This is not a flame extinguisher nor a flame suppression. The result is that the flammable cloud is transformed into a mixture of flammable product, air and flame acceleration suppression product. In case of ignition the maximum potential effect is reduced from a VCE into a “bad” burning flash fire. It means that in case of ignition the flammable gas burns without explosion. An advantage is that the flammable gas has disappeared. The present invention concerns the release of flammable material in open air.